Nanoparticles can provide a wide variety of desirable properties, among them light emission, magnetism, and electrical conductivity or semiconductivity. However, combinations of these properties can be difficult to achieve in a single nanoparticle. For example, semiconductor nanocrystals can provide narrow band light emission at selected wavelengths spanning the visible and IR spectrum. However, a single nanocrystal emits at only one wavelength; and, typically, such semiconductor nanocrystals are nonmagnetic. There is a need for multifunctional nanoparticles that can combine one or more constituent nanoparticles (and their advantageous properties) in a single nanoparticle.